One of the things I enjoy most about shows like Storage Week, sitting through many dozens of presentations on energy storage, is the breadth of perspective on the subject of clean energy. We all know that ultimately, storage is 100% required if we are to achieve the high rates of penetration we’d all like to see. That, of course, is a function of intermittency — dealing with fact that the sun shines only during the day, while the wind blows hardest at night, when the demand is at its lowest. (70% of the total wind energy in California happens at night.)

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But here are a few additional ways of looking at storage. A great deal of attention in managing the electrical grid in any given region is placed on dealing with peak consumption on a daily basis — and especially with the few hours per year that represent the absolute highest peaks that occur during the summer’s hottest afternoons. But grid managers’ dealings with load fluctuations and resource availability are not occasional incidents. In one region of the country, the spreadsheet that lists the purchase of ancillary services, those that are necessary to provide the precisely correct amount of power, has 850,000 rows (i.e., purchases) annually.

Thus, from one important perspective, energy storage solutions compete against gas-fired peaker plants, those facilities that can be ramped up and down very quickly to meet peak demand. How quickly? There are places in the US where weather conditions change dramatically and 900 MW of wind goes to 200 MW in half an hour. And wind is far more predictable than solar, where a cloud can form and blow over a solar field in a matter of minutes.